Cause A virus complex consisting of Raspberry bushy dwarf virus (RBDV) and Raspberry leaf mottle virus (RLMV) or Raspberry latent virus (RpLV). The cultivar 'Meeker' had more severe growth reductions when infected by RBDV and RLMV; whereas crumbly fruit was more prominent when infected by RBDV and RpLV or the three viruses together (RBDV, RLMV and RpLV). RBDV is spread by pollen while the other two are aphid vectored. RLMV spread rate is much higher than that of RpLV, which needs a 6-7 day period in the aphid to become transmissible. The disease can be found on many red and black raspberry cultivars as well as 'Boysenberry', 'Loganberry' and 'Marionberry' blackberries. Entire fields may become infected with the virus within 3-5 years of planting, depending on inoculum pressure from adjacent fields. The fruit from infected plants often will not make IQF grade and is sold as a lower value produce for juice, jam or puree. Since pollen is infected with RBDV honeybees play an important role in moving infected pollen from plant to plant.
A survey of RpLV and RLMV in Washington and Oregon revealed that the two viruses are present at high incidence in northern Washington; whereas the incidence in southern Washington and Oregon, where crumbly fruit is not a serious problem, was considerably lower.
Symptoms The virus complex may not produce symptoms on the foliage of many cultivars but may cause crumbly fruit as in 'Meeker'. Many drupelets abort which causes the fruit to crumble at harvest, resulting in significant reductions of yield and fruit quality. On 'Puyallup', bright yellow areas along the leaf's main and smaller veins give the leaves a "network" appearance. Severely affected leaves are almost completely bright yellow. In some red raspberry cultivars, faint ring and line patterns develop on leaves. The disease reduces growth and fruit yield in 'Meeker' and 'Canby' red raspberry but the major impact is a reduction in fruit quality. In the black raspberry 'Munger', both reduced growth and crumbly fruit occur.
- Use certified planting stock.
- 'Willamette' and 'Chilcotin' red raspberries are immune to raspberry bushy dwarf infection. 'Haida', 'Comox', and 'Heritage' are moderately resistant.
- Plant in large blocks to slow movement into new plants, especially if fields in the immediate area are infected.
Reference Quito-Avila, D. F. 2011. Impact of Raspberry bushy dwarf virus, Raspberry leaf mottle virus, and Raspberry latent virus on Plant Growth and Fruit Crumbliness in Red Raspberry (Rubus ideaus L.) 'Meeker'. PhD thesis. Oregon State University.